Add GamepadService, owns 1 gamepad bg thread

content/browser/gamepad/gamepad_provider.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <cmath>
 #include <set>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "base/task.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_restrictions.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/browser/gamepad/gamepad_provider.h"
 #include "content/browser/gamepad/data_fetcher.h"
 #include "content/common/gamepad_messages.h"
 
 #if defined(OS_WIN)
 #include "content/browser/gamepad/data_fetcher_win.h"
 #endif
 
 namespace content {
 
-GamepadProvider* GamepadProvider::instance_ = NULL;
-
 // Define the default data fetcher that GamepadProvider will use if none is
 // supplied. (GamepadPlatformDataFetcher).
 #if defined(OS_WIN)
 
 typedef GamepadDataFetcherWindows GamepadPlatformDataFetcher;
 
 #else
 
 class GamepadEmptyDataFetcher : public GamepadDataFetcher {
  public:
   void GetGamepadData(WebKit::WebGamepads* pads, bool) {
     pads->length = 0;
   }
 };
 typedef GamepadEmptyDataFetcher GamepadPlatformDataFetcher;
 
 #endif
 
 GamepadProvider::GamepadProvider(GamepadDataFetcher* fetcher)
-    : creator_loop_(MessageLoop::current()->message_loop_proxy()),
+    : is_paused_(false),
+      devices_changed_(true),
       provided_fetcher_(fetcher),
-      devices_changed_(true),
       ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)) {
   size_t data_size = sizeof(GamepadHardwareBuffer);
   base::SystemMonitor* monitor = base::SystemMonitor::Get();
   if (monitor)
     monitor->AddDevicesChangedObserver(this);
   gamepad_shared_memory_.CreateAndMapAnonymous(data_size);
   GamepadHardwareBuffer* hwbuf = SharedMemoryAsHardwareBuffer();
   memset(hwbuf, 0, sizeof(GamepadHardwareBuffer));
+
+  polling_thread_.reset(new base::Thread("Gamepad polling thread"));
+  polling_thread_->Start();
+
+  MessageLoop* polling_loop = polling_thread_->message_loop();
+  polling_loop->PostTask(
+      FROM_HERE,
+      base::Bind(&GamepadProvider::DoInitializePollingThread, this));
 }
 
 GamepadProvider::~GamepadProvider() {
   base::SystemMonitor* monitor = base::SystemMonitor::Get();
   if (monitor)
     monitor->RemoveDevicesChangedObserver(this);
-  Stop();
+
+  polling_thread_.reset();
+  data_fetcher_.reset();
 }
 
 base::SharedMemoryHandle GamepadProvider::GetRendererSharedMemoryHandle(
     base::ProcessHandle process) {
   base::SharedMemoryHandle renderer_handle;
   gamepad_shared_memory_.ShareToProcess(process, &renderer_handle);
   return renderer_handle;
 }
 
-void GamepadProvider::OnDevicesChanged() {
-  devices_changed_ = true;
+void GamepadProvider::Pause() {
+  base::AutoLock lock(is_paused_lock_);
+  is_paused_ = true;
 }
 
-void GamepadProvider::Start() {
-  DCHECK(MessageLoop::current()->message_loop_proxy() == creator_loop_);
-
-  if (polling_thread_.get())
-    return;
-
-  polling_thread_.reset(new base::Thread("Gamepad polling thread"));
-  if (!polling_thread_->Start()) {
-    LOG(ERROR) << "Failed to start gamepad polling thread";
-    polling_thread_.reset();
-    return;
+void GamepadProvider::Resume() {
+  {
+    base::AutoLock lock(is_paused_lock_);
+    if (!is_paused_)
+        return;
+    is_paused_ = false;
   }
 
   MessageLoop* polling_loop = polling_thread_->message_loop();
   polling_loop->PostTask(
       FROM_HERE,
-      base::Bind(&GamepadProvider::DoInitializePollingThread, this));
+      base::Bind(&GamepadProvider::ScheduleDoPoll, this));
 }
 
-void GamepadProvider::Stop() {
-  DCHECK(MessageLoop::current()->message_loop_proxy() == creator_loop_);
-
-  polling_thread_.reset();
-  data_fetcher_.reset();
+void GamepadProvider::OnDevicesChanged() {
+  base::AutoLock lock(devices_changed_lock_);
+  devices_changed_ = true;
 }
 
 void GamepadProvider::DoInitializePollingThread() {
   DCHECK(MessageLoop::current() == polling_thread_->message_loop());
 
   if (!provided_fetcher_.get())
     provided_fetcher_.reset(new GamepadPlatformDataFetcher);
 
   // Pass ownership of fetcher to provider_.
   data_fetcher_.swap(provided_fetcher_);
 
   // Start polling.
   ScheduleDoPoll();
 }
 
 void GamepadProvider::DoPoll() {
   DCHECK(MessageLoop::current() == polling_thread_->message_loop());
+  bool changed;
   GamepadHardwareBuffer* hwbuf = SharedMemoryAsHardwareBuffer();
 
   ANNOTATE_BENIGN_RACE_SIZED(
       &hwbuf->buffer,
       sizeof(WebKit::WebGamepads),
       "Racey reads are discarded");
 
+  {
+    base::AutoLock lock(devices_changed_lock_);
+    changed = devices_changed_;
+    devices_changed_ = false;
+  }
+
   // Acquire the SeqLock. There is only ever one writer to this data.
   // See gamepad_hardware_buffer.h.
   hwbuf->sequence.WriteBegin();
-  data_fetcher_->GetGamepadData(&hwbuf->buffer, devices_changed_);
+  data_fetcher_->GetGamepadData(&hwbuf->buffer, changed);
   hwbuf->sequence.WriteEnd();
-  devices_changed_ = false;
+
   // Schedule our next interval of polling.
   ScheduleDoPoll();
 }
 
 void GamepadProvider::ScheduleDoPoll() {
   DCHECK(MessageLoop::current() == polling_thread_->message_loop());
 
+  {
+    base::AutoLock lock(is_paused_lock_);
+    if (is_paused_)
+      return;
+  }
+
   MessageLoop::current()->PostDelayedTask(
       FROM_HERE,
       base::Bind(&GamepadProvider::DoPoll, weak_factory_.GetWeakPtr()),
       kDesiredSamplingIntervalMs);
 }
 
 GamepadHardwareBuffer* GamepadProvider::SharedMemoryAsHardwareBuffer() {
   void* mem = gamepad_shared_memory_.memory();
   DCHECK(mem);
   return static_cast<GamepadHardwareBuffer*>(mem);
 }
 
 }  // namespace content